Preparation And Properties Of Double Layered Photoanodic Films For Dye-Sensitized Solar Cells

Dye-sensitized solar cells?DSSCs?with easy processing and high theoretical efficiency have had a great progress in recent years.While,the amounts of dye loaded,the transportation of the charge,and the properties of light scattering are the main elements in affecting the further development of DSSCs.In this paper,aiming to improve the photovoltaic performance of DSSCs,TiO₂ with different morphologies are investigated to enhance the light scattering and accelerate the photoelectrons transportation.The details are as below:TiO₂ hollow spheres were prepared by hydrothermal treatment.The morphology,structure,and diffuse reflection performance of TiO₂ hollow spheres were characterizationed by FESEM,TEM,XRD,and diffuse reflection spectrum.The results showed that TiO₂ hollow spheres with good scattering performance made of anatase polyhedron.The single layered photoanodic film made of hollow spheres and the double layered structure constituted of P25 and hollow spheres were fabricated by electronspray.The results showed that the power conversion efficiency?PCE?of double layered P25-hollow spheres was 2.96%,which enhanced about 28.0% compared with single layered hollow spheres with the PCE of 2.13%.Which were attributed to P25 with large specific surface area and hollow spheres with excellent scattering performance.Therefore,the photoelectric property of double layered phtoanodic film made of P25 and hollow spheres was higher than that of single layered structure made of hollow spheres.TiO₂ microspheres made of nanosheets?sheets-pheres?can be obtained by hydrothermal method.TiO₂ nanorod?NR?can be obtained by electrospinning and ultrasonic processing.The results of FESEM,TEM and XRD showed that sheet-spheres with uniform sizes were ordered accumulation by nanosheets.The photoanodic films of single layered sheet-spheres and double layered were prepared by electrospray.The results showed that the DSSCs of single layered structure with a short-current density of 11.43 mA cm-2,an open circuit voltage of 770 mV,and the PCE of 4.14% were obtained.While the PCE of double layered structure of P25-sheet-spheres and P25/NR-sheet-spheres were 5.36% and 5.99%,respectively.This was attributed to the introduction of P25 with large amounts of dye adsorbtion.Meanwhile,the added of NR could be acted as the direct way for electron transfer and inhibited the charge recombination.Two kinds of TiO₂ microspheres?TMS?with average diameter of 1500 nm but different surface were fabricated by solvothermal method from different Ti source.The effect of different TMS on the light harvesting and photovoltaic performance of DSSCs had been investigated.The UV-Vis diffusion reflectance and absorption spectra of N719 dye solutions detached from the anodes measurement proved that the TMS showed dual functions of light scattering and dye-adsorption,which was an important functional material in DSSCs.The results showed that the TMS made from titanium?IV?isopropoxide with rough surface?TMSR?exhibited better photovoltaic performance than that of TMS made from tetrabutyl titanate with smooth surface?TMSS?.The power conversion efficiency?PCE?of TMSR was 5.54%,which was higher than that of TMSS?4.10%?,but still lower than that of P25?5.75%?.In order to further improve the photovoltaic performance,the double layered DSSCs made of P25 as an underlayer and TMS as a light-scattering layer?P25-TMS?were fabricated.The photovoltaic performance of double layered DSSCs were higher than that of the singer layered DSSCs with similar thickness.Meanwhile,the P25-TMSR showed the best power conversion efficiency of 7.62% with a large short-current density of 22.79 mA cm-2,and a Voc of 772 mV,and this was mainly attributed to the large specific surface area,superior light scattering ability,and fast electron transport.